Sundon is one of the ancient parishes of Bedfordshire. The parish contains two main settlements, Upper Sundon and Lower Sundon. The church is in Lower Sundon, but Upper Sundon is the larger settlement.

Because of changes to its boundary, the parish no longer includes Sundon Park (which is now an area of Luton) or the "Sundon Substation" of the National Grid for electricity (which lies west of the railway, near the village of Chalton).